1 Import Libraries

List of used packages: knitr dplyr ggplot2 broom reshape2 janitor plm pwt9 quarto renv shiny targets testthat tidyverse tibble usethis rio lubridate purrr Hmisc plotly hrbrthemes xts seasonal tsbox forecast tseries plotly ggridges shades urca

colorize <- function(x, color) {
  if (knitr::is_latex_output()) {
    sprintf("\\textcolor{%s}{%s}", color, x)
  } else if (knitr::is_html_output()) {
    sprintf("<span style='color: %s;'>%s</span>", color,
      x)
  } else x
}
#webshot::install_phantomjs()

2 Introduction

2.1 Describe Dataset

The dataset used for this project is Daily Delhi Climate, which consists of the following columns: 1. date: Date of format YYYY-MM-DD starting from “2013-01-01” and ending in “2017-01-01”.
2. meantemp: Mean temperature averaged out from multiple 3 hour intervals in a day.
3. humidity: Humidity value for the day (units are grams of water vapor per cubic meter volume of air).
4. wind_speed: Wind speed measured in kmph.
5. mean_pressure: Pressure reading of weather (measure in atm)

Q1. How can I find out if analyzing meantemp indvidiually (univariate) suffices, or if including other columns and perform a multivariate analysis would worth the effort to find more meaninful patterns and forecasts?

2.2 Goal and Procedure

The goal of this project is to analyze and forecast the mean temperature Delhi, which is recorded in the meantemp column. For this, after importing the dataset, outliers are removed in Preprocessing Section section. Then meantemp column is assigned to a time series object in Construct Time Series section for further processing, analysis, and forecast. After detecting seasonalities using plots, the time series is seasonally adjusted using X13-ARIMA-SEATS. Then, remaining trend is removed in detrend.

Before forecasting the time series, I check for stationarity of time series, as stationarity is an assumption in ARIMA model. For this purpose, unit root tests are applied in Stationarity section.

Finally, I used ARIMA model to forecast the time series in Forecast Time Series section.

df_train <- read_csv("data/DailyDelhiClimateTrain.csv")
## Rows: 1462 Columns: 5
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## dbl  (4): meantemp, humidity, wind_speed, meanpressure
## date (1): date
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.
df_test <- read_csv("data/DailyDelhiClimateTest.csv")
## Rows: 114 Columns: 5
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## dbl  (4): meantemp, humidity, wind_speed, meanpressure
## date (1): date
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.
summary(df_train)
##       date               meantemp        humidity        wind_speed    
##  Min.   :2013-01-01   Min.   : 6.00   Min.   : 13.43   Min.   : 0.000  
##  1st Qu.:2014-01-01   1st Qu.:18.86   1st Qu.: 50.38   1st Qu.: 3.475  
##  Median :2015-01-01   Median :27.71   Median : 62.62   Median : 6.222  
##  Mean   :2015-01-01   Mean   :25.50   Mean   : 60.77   Mean   : 6.802  
##  3rd Qu.:2016-01-01   3rd Qu.:31.31   3rd Qu.: 72.22   3rd Qu.: 9.238  
##  Max.   :2017-01-01   Max.   :38.71   Max.   :100.00   Max.   :42.220  
##   meanpressure     
##  Min.   :  -3.042  
##  1st Qu.:1001.580  
##  Median :1008.563  
##  Mean   :1011.105  
##  3rd Qu.:1014.945  
##  Max.   :7679.333
df_train |> describe()
## df_train 
## 
##  5  Variables      1462  Observations
## --------------------------------------------------------------------------------
## date 
##          n    missing   distinct       Info       Mean        Gmd        .05 
##       1462          0       1462          1 2015-01-01      487.7 2013-03-15 
##        .10        .25        .50        .75        .90        .95 
## 2013-05-27 2014-01-01 2015-01-01 2016-01-01 2016-08-07 2016-10-19 
## 
## lowest : 2013-01-01 2013-01-02 2013-01-03 2013-01-04 2013-01-05
## highest: 2016-12-28 2016-12-29 2016-12-30 2016-12-31 2017-01-01
## --------------------------------------------------------------------------------
## meantemp 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##     1462        0      617        1     25.5    8.331    12.51    14.62 
##      .25      .50      .75      .90      .95 
##    18.86    27.71    31.31    33.71    35.43 
## 
## lowest :  6.000000  7.000000  7.166667  7.400000  8.666667
## highest: 38.200000 38.272727 38.428571 38.500000 38.714286
## --------------------------------------------------------------------------------
## humidity 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##     1462        0      897        1    60.77    18.96    29.00    36.21 
##      .25      .50      .75      .90      .95 
##    50.38    62.62    72.22    81.85    86.99 
## 
## lowest :  13.42857  15.85714  18.46667  19.00000  19.50000
## highest:  96.12500  96.62500  96.85714  98.00000 100.00000
## --------------------------------------------------------------------------------
## wind_speed 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##     1462        0      736        1    6.802    4.878    0.925    1.625 
##      .25      .50      .75      .90      .95 
##    3.475    6.222    9.238   12.608   14.813 
## 
## lowest :  0.0000000  0.4625000  0.4750000  0.5285714  0.6166667
## highest: 27.7750000 30.6857143 33.3250000 34.4875000 42.2200000
## --------------------------------------------------------------------------------
## meanpressure 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##     1462        0      626        1     1011    22.92    996.8    998.1 
##      .25      .50      .75      .90      .95 
##   1001.6   1008.6   1014.9   1017.8   1019.3 
## 
## lowest :   -3.041667   12.045455  310.437500  633.900000  938.066667
## highest: 1022.125000 1023.000000 1350.296296 1352.615385 7679.333333
##                                                     
## Value          0   300   600   900  1000  1400  7700
## Frequency      2     1     1     2  1453     2     1
## Proportion 0.001 0.001 0.001 0.001 0.994 0.001 0.001
## 
## For the frequency table, variable is rounded to the nearest 100
## --------------------------------------------------------------------------------

3 Visualize Data

Below we can see interactive plot of the time series.

p <- df_train |>
  ggplot( aes(x=date, y=meantemp)) +
    geom_area(fill="#69b3a2", alpha=0.5) +
    geom_line(color="#69b3a2") +
    ylab("bitcoin price ($)") +
    theme_ipsum()

# Turn it interactive with ggplotly
p <- ggplotly(p)
#p
p

4 Preprocessing

We can detect an outlier at the last observation (last row of dataframe). It causes an abrupt decrease in value of temperature. This would lead to problems in further analysis I will proceed and also when I later apply functions on the time series. Therefore, I replace the last observation’s value with its previous one.

Q2. Is imputing with the last observation the right approach here? Or is preferrable that I use median of last n (rows) for instance? Maybe it won’t matter, as when I aggregate data (per week, month, week, etc.), I remove the last observation.

previous_value <- df_train$meantemp[df_train$date == as.Date('2016-12-31')]

df_train$meantemp[df_train$date == as.Date('2017-01-01')]<- previous_value 
#df_train <- head(df_train, -1)
head(df_train)
## # A tibble: 6 × 5
##   date       meantemp humidity wind_speed meanpressure
##   <date>        <dbl>    <dbl>      <dbl>        <dbl>
## 1 2013-01-01    10        84.5       0           1016.
## 2 2013-01-02     7.4      92         2.98        1018.
## 3 2013-01-03     7.17     87         4.63        1019.
## 4 2013-01-04     8.67     71.3       1.23        1017.
## 5 2013-01-05     6        86.8       3.7         1016.
## 6 2013-01-06     7        82.8       1.48        1018
tail(df_train)
## # A tibble: 6 × 5
##   date       meantemp humidity wind_speed meanpressure
##   <date>        <dbl>    <dbl>      <dbl>        <dbl>
## 1 2016-12-27     16.8     67.6       8.34        1017.
## 2 2016-12-28     17.2     68.0       3.55        1016.
## 3 2016-12-29     15.2     87.9       6           1017.
## 4 2016-12-30     14.1     89.7       6.27        1018.
## 5 2016-12-31     15.1     87         7.32        1016.
## 6 2017-01-01     15.1    100         0           1016

Let us how the plot looks after removing the outlier:

p <- df_train |>
  ggplot( aes(x=date, y=meantemp)) +
    geom_area(fill="#69b3a2", alpha=0.5) +
    geom_line(color="#69b3a2") +
    ylab("bitcoin price ($)") +
    theme_ipsum()

# Turn it interactive with ggplotly
p <- ggplotly(p)
#p
p

Find if there is any missing dates

date_range <- seq(min(df_train$date), max(df_train$date), by = 1) 
date_range[!date_range %in% df_train$date] 
## Date of length 0

5 Prepare Test Set

summary(df_test)
##       date               meantemp        humidity       wind_speed    
##  Min.   :2017-01-01   Min.   :11.00   Min.   :17.75   Min.   : 1.387  
##  1st Qu.:2017-01-29   1st Qu.:16.44   1st Qu.:39.62   1st Qu.: 5.564  
##  Median :2017-02-26   Median :19.88   Median :57.75   Median : 8.069  
##  Mean   :2017-02-26   Mean   :21.71   Mean   :56.26   Mean   : 8.144  
##  3rd Qu.:2017-03-26   3rd Qu.:27.71   3rd Qu.:71.90   3rd Qu.:10.069  
##  Max.   :2017-04-24   Max.   :34.50   Max.   :95.83   Max.   :19.314  
##   meanpressure 
##  Min.   :  59  
##  1st Qu.:1007  
##  Median :1013  
##  Mean   :1004  
##  3rd Qu.:1017  
##  Max.   :1023
df_test |> describe()
## df_test 
## 
##  5  Variables      114  Observations
## --------------------------------------------------------------------------------
## date 
##          n    missing   distinct       Info       Mean        Gmd        .05 
##        114          0        114          1 2017-02-26      38.33 2017-01-06 
##        .10        .25        .50        .75        .90        .95 
## 2017-01-12 2017-01-29 2017-02-26 2017-03-26 2017-04-12 2017-04-18 
## 
## lowest : 2017-01-01 2017-01-02 2017-01-03 2017-01-04 2017-01-05
## highest: 2017-04-20 2017-04-21 2017-04-22 2017-04-23 2017-04-24
## --------------------------------------------------------------------------------
## meantemp 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##      114        0      105        1    21.71    7.226    13.22    14.75 
##      .25      .50      .75      .90      .95 
##    16.44    19.88    27.71    31.00    32.67 
## 
## lowest : 11.00000 11.72222 11.78947 12.11111 13.04167
## highest: 32.90000 33.50000 34.00000 34.25000 34.50000
## --------------------------------------------------------------------------------
## humidity 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##      114        0      109        1    56.26    21.97    26.74    29.49 
##      .25      .50      .75      .90      .95 
##    39.62    57.75    71.90    78.42    82.20 
## 
## lowest : 17.75000 19.42857 21.12500 24.12500 26.00000
## highest: 83.52632 84.44444 85.86957 91.64286 95.83333
## --------------------------------------------------------------------------------
## wind_speed 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##      114        0      109        1    8.144    4.031    2.842    3.715 
##      .25      .50      .75      .90      .95 
##    5.564    8.069   10.069   13.464   14.353 
## 
## lowest :  1.387500  1.625000  1.854545  1.950000  2.100000
## highest: 14.384615 15.512500 16.662500 17.590000 19.314286
## --------------------------------------------------------------------------------
## meanpressure 
##        n  missing distinct     Info     Mean      Gmd      .05      .10 
##      114        0      109        1     1004    23.16     1002     1004 
##      .25      .50      .75      .90      .95 
##     1007     1013     1017     1019     1021 
## 
## lowest :   59.000  998.625  999.875 1000.875 1001.600
## highest: 1021.375 1021.556 1021.789 1021.958 1022.810
##                                   
## Value         60  1000  1010  1020
## Frequency      1    14    53    46
## Proportion 0.009 0.123 0.465 0.404
## 
## For the frequency table, variable is rounded to the nearest 10
## --------------------------------------------------------------------------------
xts_test_meantemp <- xts(df_test$meantemp, order.by=df_test$date, "%Y-%m-%d")
head(xts_test_meantemp)
##                [,1]
## 2017-01-01 15.91304
## 2017-01-02 18.50000
## 2017-01-03 17.11111
## 2017-01-04 18.70000
## 2017-01-05 18.38889
## 2017-01-06 19.31818
tail(xts_test_meantemp)
##              [,1]
## 2017-04-19 33.500
## 2017-04-20 34.500
## 2017-04-21 34.250
## 2017-04-22 32.900
## 2017-04-23 32.875
## 2017-04-24 32.000
ts_plot(xts_test_meantemp)

ts_test_meantemp <- ts_ts(xts_test_meantemp)
xts_week_test_meantemp <- apply.weekly(xts_test_meantemp,sum)
ts_week_test_meantemp <- ts_ts(xts_week_test_meantemp)
ts_plot(xts_week_test_meantemp)

6 Time Series Analysis

6.1 Construct Time Series

Now we use the meantemp column to create our time series data. I assigned the time series to xts objects. But since many functions later require ts object, each time I define an xts, I also convert it to ts object using tsbox::ts_ts

min(df_train$date)
## [1] "2013-01-01"
max(df_train$date)
## [1] "2017-01-01"
#ts_train <- zoo(df_train$meantemp, df_train$date)

xts_train_meantemp <- xts(df_train$meantemp, order.by=df_train$date, "%Y-%m-%d")
class(xts_train_meantemp)
## [1] "xts" "zoo"
head(xts_train_meantemp)
##                 [,1]
## 2013-01-01 10.000000
## 2013-01-02  7.400000
## 2013-01-03  7.166667
## 2013-01-04  8.666667
## 2013-01-05  6.000000
## 2013-01-06  7.000000
tail(xts_train_meantemp)
##                [,1]
## 2016-12-27 16.85000
## 2016-12-28 17.21739
## 2016-12-29 15.23810
## 2016-12-30 14.09524
## 2016-12-31 15.05263
## 2017-01-01 15.05263
# convert xts to ts

## Create a daily Date object for ts
#inds <- seq(as.Date("2013-01-01"), as.Date("2017-01-01"), by = "day")

#set.seed(25)
#ts_train <- ts(df_train$meantemp,     # random data
#           start = c(2013, as.numeric(format(inds[1], "%j"))),
#           frequency = 365)


#ts_train <- ts(df_train$meantemp, start = decimal_date(ymd("2013-01-01")), frequency = 365.25 / 7)

Convert XTS objects to TS objects:

ts_train_meantemp <-ts_ts(xts_train_meantemp)
head(ts_train_meantemp)
## Time Series:
## Start = 2013 
## End = 2013.01368953503 
## Frequency = 365.2425 
## [1] 10.000000  7.400000  7.166667  8.666667  6.000000  7.000000
tail(ts_train_meantemp)
## Time Series:
## Start = 2016.98639260218 
## End = 2017.00008213721 
## Frequency = 365.2425 
## [1] 16.85000 17.21739 15.23810 14.09524 15.05263 15.05263

I plot a static plot as well:

ts_plot(xts_train_meantemp)

## Seasonality {#seas}

From the initial plot I judge that there is yearly seasonality. For more delicate observation to find if there is more granular periods of seasonality, I use seasonality plots. Before that, I aggregate data weekly, monthly, and quarterly.

6.1.1 Seasonality Plots

# Weekly mean temperature
xts_week_train_meantemp <- apply.weekly(xts_train_meantemp,sum)
ts_week_train_meantemp <-ts_ts(xts_week_train_meantemp)

# Monthly mean temperature
xts_mon_train_meantemp <- aggregate(xts_train_meantemp, by=as.yearmon, FUN=sum)
ts_mon_train_meantemp <-ts_ts(xts_mon_train_meantemp)

# Quarterly mean temperature
xts_quar_train_meantemp <- aggregate(xts_train_meantemp, as.yearqtr, FUN=sum)
ts_quar_train_meantemp <-ts_ts(xts_quar_train_meantemp)


# Yearly mean temperate
as.year <- function(x) as.integer(as.yearmon(x))
xts_year_train_meantemp <- aggregate(xts_train_meantemp, by=as.year, FUN=sum)
#ts_year_train_meantemp <-ts_ts(xts_year_train_meantemp)
#xts_year_train_meantemp[1]

The year 2017 has only one observation, so I remove it from all the aggregated datasets. I couldn’t do it before aggregating, otherwise I would have confronted the error Error: series has no regular pattern.

xts_week_train_meantemp <- head(xts_week_train_meantemp, -1)
xts_mon_train_meantemp <- head(xts_mon_train_meantemp, -1)
xts_quar_train_meantemp <- head(xts_quar_train_meantemp, -1)

ts_week_train_meantemp <- head(ts_week_train_meantemp, -1)
ts_mon_train_meantemp <- head(ts_mon_train_meantemp, -1)
ts_quar_train_meantemp <- head(ts_quar_train_meantemp, -1)
#options(repr.plot.width = 7, repr.plot.height =20)
forecast::ggseasonplot(ts_mon_train_meantemp, year.labels=TRUE, year.labels.left=TRUE, labelgap = 0.1) +
  ylab("degree") +
  ggtitle("Seasonal plot: Monthly Mean Temperature")

forecast::ggseasonplot(ts_mon_train_meantemp, year.labels=TRUE, year.labels.left=TRUE, labelgap = 0.1, polar=TRUE) +
  ylab("degree") +
  ggtitle("Polar Seasonal plot: Monthly Mean Temperature")

#options(repr.plot.width = 7, repr.plot.height =20)
forecast::ggseasonplot(ts_quar_train_meantemp, year.labels=TRUE, year.labels.left=TRUE, labelgap = 0.1) +
  ylab("degree") +
  ggtitle("Seasonal plot: Quarterly Mean Temperature")

forecast::ggseasonplot(ts_quar_train_meantemp, year.labels=TRUE, year.labels.left=TRUE, labelgap = 0.1, polar=TRUE) +
  ylab("degree") +
  ggtitle("Polar Seasonal plot: Quarterly Mean Temperature")

### Deseasonalize {#deseas}

If I need to remove different periods of seasonality together, I would need to use the forecast:msts function. For instance in below I remove weekly and yearly seasonality together.

des_ts_train_meantemp <- msts(xts_train_meantemp,seasonal.periods = c(7,365))
#head(des_xts_train)
#library(tsbox)
#ts_train <-ts_ts(xts_train)
#ts_train

class(des_ts_train_meantemp)
## [1] "msts" "ts"

However, since its output had an unfamiliar and weird shape to me, and also since I wasn’t sure it uses the state-of-the-art X13 decomposition, I incorporated the X-13ARIMA-SEATS using seasonal:seas function. However, it has some limitations, as stated in the package’s reference manua. For instance, the number of observations must not exceed 780. Nor should maximum seasonal period exceed 12. That is why I couldn’t use original data ts_train and also the weekly aggregated data ts_week_train, as I would confront the error Seasonal period too large. The only possible aggregated data with highest frequency possible was monthly aggregated, ts_mon_train. However, I am concerned that I would lose significant pattern and information with this amount of aggregation.

Q3. If you could kindly share your viewpoint here, it would be very helpful for me to ensure how to proceed.

length(xts_train_meantemp)
## [1] 1462
length(ts_train_meantemp)
## [1] 1462
length(xts_train_meantemp)
## [1] 1462
nowXTS <-ts_xts(ts_train_meantemp)
length(nowXTS)
## [1] 1462
length(ts_week_train_meantemp)
## [1] 208
plot(ts_week_train_meantemp)

length(ts_week_train_meantemp)
## [1] 208
plot(ts_train_meantemp)

length(ts_train_meantemp)
## [1] 1462
plot(ts_mon_train_meantemp)

length(ts_mon_train_meantemp)
## [1] 48
m <- seas(ts_mon_train_meantemp)
ts_train_adj_meantemp <- final(m)
#ts_train_adj
length(ts_train_adj_meantemp)
## [1] 48
m <- seas(ts_mon_train_meantemp)
ts_train_adj_meantemp <- final(m)
#ts_train_adj
length(ts_train_adj_meantemp)
## [1] 48
plot(ts_train_adj_meantemp)

Plot original data along with trend and seasonally adjusted data

#ts_train
#series(m, "forecast.forecasts")
#out(m)
#seasadj(m)
autoplot(ts_mon_train_meantemp, series="Original Data") +
autolayer(trendcycle(m), series="Trend") +
autolayer(seasadj(m), series="Seasonally Adjusted") +
xlab("Year") + ylab("Mean Temperature") +
ggtitle("Mean Temperature Decomposed using X13") +
scale_colour_manual(values=c("gray","blue","red"),
           breaks=c("Original Data","Seasonally Adjusted","Trend"))

#ap < ggplotly(ap)

6.2 Detrend

In the seasonally adjusted time series ts_train_adj, I detected a trend, therefore I detrend it using differencing.

#ts_train_adj_meantemp |> log() |> nsdiffs(alpha=0.01) -> ts_train_adj_det_meantemp
ts_train_adj_meantemp |> log() |> diff() -> ts_train_adj_det_meantemp
plot(ts_train_adj_det_meantemp)

#plot(d)

6.3 Correlation Plots

  1. Weekly aggregated of original time series
ggAcf(ts_week_train_meantemp, lag=50)

pacf (ts_week_train_meantemp, lag=50, pl = TRUE)

  1. Seasonally Adjusted
ggAcf(ts_train_adj_meantemp, lag=10)

pacf (ts_train_adj_meantemp, lag=10, pl = TRUE)

  1. Seasonally Adjusted and Detrended
ggAcf(ts_train_adj_det_meantemp, lag=10)

pacf (ts_train_adj_det_meantemp, lag=10, pl = TRUE)

6.4 Testing Stationarity: Unit Root Tests

6.4.1 ADF

  1. Original Time Series and its weekly adjusted
ts_train_meantemp |> adf.test()
## 
##  Augmented Dickey-Fuller Test
## 
## data:  ts_train_meantemp
## Dickey-Fuller = -1.9871, Lag order = 11, p-value = 0.5838
## alternative hypothesis: stationary
ts_week_train_meantemp |> adf.test()
## 
##  Augmented Dickey-Fuller Test
## 
## data:  ts_week_train_meantemp
## Dickey-Fuller = -3.8729, Lag order = 5, p-value = 0.01651
## alternative hypothesis: stationary
  1. Seasonally Adjusted
ts_train_adj_meantemp |> adf.test() 
## 
##  Augmented Dickey-Fuller Test
## 
## data:  ts_train_adj_meantemp
## Dickey-Fuller = -2.5897, Lag order = 3, p-value = 0.3386
## alternative hypothesis: stationary
  1. Seasonally Adjusted and Detrended
ts_train_adj_det_meantemp |> adf.test() 
## Warning in adf.test(ts_train_adj_det_meantemp): p-value smaller than printed p-
## value
## 
##  Augmented Dickey-Fuller Test
## 
## data:  ts_train_adj_det_meantemp
## Dickey-Fuller = -4.698, Lag order = 3, p-value = 0.01
## alternative hypothesis: stationary

6.4.2 KPSS

  1. Original Time Series and also its weekly aggregated
ts_train_meantemp |> ur.kpss() |> summary()
## 
## ####################### 
## # KPSS Unit Root Test # 
## ####################### 
## 
## Test is of type: mu with 7 lags. 
## 
## Value of test-statistic is: 0.5812 
## 
## Critical value for a significance level of: 
##                 10pct  5pct 2.5pct  1pct
## critical values 0.347 0.463  0.574 0.739
ts_week_train_meantemp |> ur.kpss() |> summary()
## 
## ####################### 
## # KPSS Unit Root Test # 
## ####################### 
## 
## Test is of type: mu with 4 lags. 
## 
## Value of test-statistic is: 0.1618 
## 
## Critical value for a significance level of: 
##                 10pct  5pct 2.5pct  1pct
## critical values 0.347 0.463  0.574 0.739
  1. Seasonally Adjusted
ts_train_adj_meantemp |> ur.kpss() |> summary()
## 
## ####################### 
## # KPSS Unit Root Test # 
## ####################### 
## 
## Test is of type: mu with 3 lags. 
## 
## Value of test-statistic is: 0.9974 
## 
## Critical value for a significance level of: 
##                 10pct  5pct 2.5pct  1pct
## critical values 0.347 0.463  0.574 0.739
  1. Seasonally Adjusted and Detrended
ts_train_adj_det_meantemp |> ur.kpss() |> summary()
## 
## ####################### 
## # KPSS Unit Root Test # 
## ####################### 
## 
## Test is of type: mu with 3 lags. 
## 
## Value of test-statistic is: 0.0595 
## 
## Critical value for a significance level of: 
##                 10pct  5pct 2.5pct  1pct
## critical values 0.347 0.463  0.574 0.739

6.4.3 Dickey–Fuller

ts_train_meantemp |> ur.df() |> summary()
## 
## ############################################### 
## # Augmented Dickey-Fuller Test Unit Root Test # 
## ############################################### 
## 
## Test regression none 
## 
## 
## Call:
## lm(formula = z.diff ~ z.lag.1 - 1 + z.diff.lag)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -9.6532 -0.8403  0.1233  1.0729  6.5542 
## 
## Coefficients:
##             Estimate Std. Error t value Pr(>|t|)    
## z.lag.1    -0.001560   0.001622  -0.962    0.336    
## z.diff.lag -0.158894   0.025836  -6.150 9.98e-10 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 1.644 on 1458 degrees of freedom
## Multiple R-squared:  0.02616,    Adjusted R-squared:  0.02483 
## F-statistic: 19.59 on 2 and 1458 DF,  p-value: 4.036e-09
## 
## 
## Value of test-statistic is: -0.9621 
## 
## Critical values for test statistics: 
##       1pct  5pct 10pct
## tau1 -2.58 -1.95 -1.62

7 Time Series Forecasting

7.1 AUTO-ARIMA

  1. Forecast original time series of meantemp, as the original data has very high frequency, which makes it unsuitable for ARMA. For this case, I set seasonal=TRUE, as in cases 3m I use data that I seasonally adjusted them already. Setting seasonal=TRUE makes the model more time-consuming.
#forecast_ts_train_meantemp = auto.arima(ts_train_meantemp,
#                            trace = TRUE, 
#                            seasonal=TRUE,
#                            stepwise=FALSE,
#                            approximation=FALSE)
#checkresiduals(forecast_ts_train_meantemp)
forecast_ts_train_meantemp <- auto.arima(ts_train_meantemp,
                            d = 1,
                            D = 1,
                            start.p = 2,
                            start.q = 3,
                            max.p = 2,
                            #max.d = 1,
                            max.q = 3,
                            start.P = 0,
                            start.Q = 0,
                            max.P = 0,
                            #max.D = 1,
                            max.Q = 0,
                            trace = TRUE, 
                            seasonal=TRUE,
                            stepwise=TRUE,
                            approximation=FALSE
                            #nmodels=
                            )
## 
##  ARIMA(2,1,3)(0,1,0)[365]                    : 4789.495
##  ARIMA(0,1,0)(0,1,0)[365]                    : 4943.724
##  ARIMA(1,1,0)(0,1,0)[365]                    : 4926.887
##  ARIMA(0,1,1)(0,1,0)[365]                    : 4920.711
##  ARIMA(1,1,3)(0,1,0)[365]                    : 4789.51
##  ARIMA(2,1,2)(0,1,0)[365]                    : Inf
##  ARIMA(1,1,2)(0,1,0)[365]                    : 4790.218
## 
##  Best model: ARIMA(2,1,3)(0,1,0)[365]
checkresiduals(forecast_ts_train_meantemp)

## 
##  Ljung-Box test
## 
## data:  Residuals from ARIMA(2,1,3)(0,1,0)[365]
## Q* = 363.76, df = 287, p-value = 0.001427
## 
## Model df: 5.   Total lags used: 292
#checkresiduals(forecast_ts_train_meantemp)
forecast_ts_train_meantemp
## Series: ts_train_meantemp 
## ARIMA(2,1,3)(0,1,0)[365] 
## 
## Coefficients:
##          ar1     ar2      ma1      ma2      ma3
##       0.0104  0.4362  -0.2760  -0.6134  -0.0888
## s.e.  0.3402  0.2577   0.3395   0.3585   0.0480
## 
## sigma^2 = 4.561:  log likelihood = -2388.71
## AIC=4789.42   AICc=4789.5   BIC=4819.41
autoplot(forecast(forecast_ts_train_meantemp))# + autolayer(xts_test_meantemp)

length(ts_test_meantemp)
## [1] 114
forecast_ts_train_meantemp |> forecast(h=114) |>
autoplot() + autolayer(ts_test_meantemp)

  1. Forecast original time series of meantemp but aggregated weekly, as the original data has very high frequency, which makes it unsuitable for ARMA. For this case, I set seasonal=TRUE, as in case 3, I use data that I seasonally adjusted them already. Setting seasonal=TRUE makes the model more time-consuming.
#forecast_ts_week_train_meantemp = auto.arima(ts_week_train_meantemp,
#                            trace = TRUE, 
#                            seasonal=TRUE,
#                            stepwise=FALSE,
#                            approximation=FALSE)
#checkresiduals(forecast_ts_week_train_meantemp)
#autoplot(forecast(ts_week_train_meantemp)) #+ autolayer(ts_week_test_meantemp)
  1. Forecast deseasonalized time series:
forecast_ts_train_adj_meantemp = auto.arima(ts_train_adj_meantemp,
                            trace = TRUE, 
                            seasonal= FALSE,
                            stepwise=FALSE,
                            approximation=FALSE)
## 
##  ARIMA(0,1,0)                               : 441.3883
##  ARIMA(0,1,0)            with drift         : 443.1154
##  ARIMA(0,1,1)                               : 429.9577
##  ARIMA(0,1,1)            with drift         : 429.5371
##  ARIMA(0,1,2)                               : 432.2379
##  ARIMA(0,1,2)            with drift         : 431.8095
##  ARIMA(0,1,3)                               : 434.4112
##  ARIMA(0,1,3)            with drift         : 433.7996
##  ARIMA(0,1,4)                               : 434.6353
##  ARIMA(0,1,4)            with drift         : Inf
##  ARIMA(0,1,5)                               : Inf
##  ARIMA(0,1,5)            with drift         : Inf
##  ARIMA(1,1,0)                               : 432.8756
##  ARIMA(1,1,0)            with drift         : 434.1589
##  ARIMA(1,1,1)                               : 432.2366
##  ARIMA(1,1,1)            with drift         : 431.7635
##  ARIMA(1,1,2)                               : 434.6252
##  ARIMA(1,1,2)            with drift         : Inf
##  ARIMA(1,1,3)                               : 436.6632
##  ARIMA(1,1,3)            with drift         : Inf
##  ARIMA(1,1,4)                               : 436.8366
##  ARIMA(1,1,4)            with drift         : Inf
##  ARIMA(2,1,0)                               : 432.5313
##  ARIMA(2,1,0)            with drift         : 433.449
##  ARIMA(2,1,1)                               : 434.5063
##  ARIMA(2,1,1)            with drift         : 433.7124
##  ARIMA(2,1,2)                               : 436.9823
##  ARIMA(2,1,2)            with drift         : Inf
##  ARIMA(2,1,3)                               : Inf
##  ARIMA(2,1,3)            with drift         : Inf
##  ARIMA(3,1,0)                               : 434.8565
##  ARIMA(3,1,0)            with drift         : 435.9464
##  ARIMA(3,1,1)                               : 436.788
##  ARIMA(3,1,1)            with drift         : Inf
##  ARIMA(3,1,2)                               : Inf
##  ARIMA(3,1,2)            with drift         : Inf
##  ARIMA(4,1,0)                               : 436.5007
##  ARIMA(4,1,0)            with drift         : 437.448
##  ARIMA(4,1,1)                               : Inf
##  ARIMA(4,1,1)            with drift         : 436.8826
##  ARIMA(5,1,0)                               : 436.434
##  ARIMA(5,1,0)            with drift         : 436.606
## 
## 
## 
##  Best model: ARIMA(0,1,1)            with drift
checkresiduals(forecast_ts_train_adj_meantemp)

## 
##  Ljung-Box test
## 
## data:  Residuals from ARIMA(0,1,1) with drift
## Q* = 7.4191, df = 9, p-value = 0.5936
## 
## Model df: 1.   Total lags used: 10
#forecast_ts_train_adj + ts_train_adj
autoplot(forecast(forecast_ts_train_adj_meantemp))

  1. Forecast deseasonalized and detrended time series:
forecast_ts_train_adj_det_meantemp = auto.arima(ts_train_adj_det_meantemp,
                            trace = TRUE, 
                            seasonal= FALSE,
                            stepwise=FALSE,
                            approximation=FALSE)
## 
##  ARIMA(0,0,0)            with zero mean     : -183.1965
##  ARIMA(0,0,0)            with non-zero mean : -181.4467
##  ARIMA(0,0,1)            with zero mean     : -195.2457
##  ARIMA(0,0,1)            with non-zero mean : -195.724
##  ARIMA(0,0,2)            with zero mean     : -192.9693
##  ARIMA(0,0,2)            with non-zero mean : -193.439
##  ARIMA(0,0,3)            with zero mean     : -190.7534
##  ARIMA(0,0,3)            with non-zero mean : -191.4021
##  ARIMA(0,0,4)            with zero mean     : -190.4085
##  ARIMA(0,0,4)            with non-zero mean : Inf
##  ARIMA(0,0,5)            with zero mean     : Inf
##  ARIMA(0,0,5)            with non-zero mean : Inf
##  ARIMA(1,0,0)            with zero mean     : -191.9675
##  ARIMA(1,0,0)            with non-zero mean : -190.6383
##  ARIMA(1,0,1)            with zero mean     : -192.971
##  ARIMA(1,0,1)            with non-zero mean : -193.4768
##  ARIMA(1,0,2)            with zero mean     : -190.5819
##  ARIMA(1,0,2)            with non-zero mean : Inf
##  ARIMA(1,0,3)            with zero mean     : -188.4672
##  ARIMA(1,0,3)            with non-zero mean : Inf
##  ARIMA(1,0,4)            with zero mean     : -188.2137
##  ARIMA(1,0,4)            with non-zero mean : Inf
##  ARIMA(2,0,0)            with zero mean     : -192.6467
##  ARIMA(2,0,0)            with non-zero mean : -191.6913
##  ARIMA(2,0,1)            with zero mean     : -190.668
##  ARIMA(2,0,1)            with non-zero mean : -191.4938
##  ARIMA(2,0,2)            with zero mean     : -188.1949
##  ARIMA(2,0,2)            with non-zero mean : Inf
##  ARIMA(2,0,3)            with zero mean     : Inf
##  ARIMA(2,0,3)            with non-zero mean : Inf
##  ARIMA(3,0,0)            with zero mean     : -190.3099
##  ARIMA(3,0,0)            with non-zero mean : -189.1897
##  ARIMA(3,0,1)            with zero mean     : -188.4346
##  ARIMA(3,0,1)            with non-zero mean : Inf
##  ARIMA(3,0,2)            with zero mean     : Inf
##  ARIMA(3,0,2)            with non-zero mean : Inf
##  ARIMA(4,0,0)            with zero mean     : -188.6455
##  ARIMA(4,0,0)            with non-zero mean : -187.6592
##  ARIMA(4,0,1)            with zero mean     : Inf
##  ARIMA(4,0,1)            with non-zero mean : -188.2978
##  ARIMA(5,0,0)            with zero mean     : -188.6625
##  ARIMA(5,0,0)            with non-zero mean : -188.4274
## 
## 
## 
##  Best model: ARIMA(0,0,1)            with non-zero mean
checkresiduals(forecast_ts_train_adj_det_meantemp)

## 
##  Ljung-Box test
## 
## data:  Residuals from ARIMA(0,0,1) with non-zero mean
## Q* = 7.1212, df = 8, p-value = 0.5236
## 
## Model df: 1.   Total lags used: 9
autoplot(forecast(forecast_ts_train_adj_det_meantemp))

Q4. I did all unit root tests and ARIMA models on all the following datasets: original time series, deseasonalized time series, and combination of deaseonalized and detrended time series. Judging by the plots, the adjusted versions performed poorly when fed to the model compared to feeding the weekly aggregated data that is fed to AUTOARIMA but with autmatic seasonality modelling of seasonality. Could you please share your viewpoint regarding this?

7.2 Vector autoregressive (VAR)

Now we model a multivariate time series by using both the columns meantemp and wind_speed.

We plot wind_speed time series first:

We use an interactive plot.

p2 <- df_train |>
  ggplot( aes(x=date, y=wind_speed)) +
    geom_area(fill="#69b3a2", alpha=0.5) +
    geom_line(color="#69b3a2") +
    ylab("bitcoin price ($)") +
    theme_ipsum()

# Turn it interactive with ggplotly
p2 <- ggplotly(p2)
#p
p2

Now we use a static plot.

#xts_train_meantemp <- xts(df_train$meantemp, order.by=df_train$date, "%Y-%m-%d")
#ts_train_meantemp <-ts_ts(xts_train_meantemp)

xts_train_windspeed <- xts(df_train$wind_speed, order.by=df_train$date, "%Y-%m-%d")
ts_train_windspeed <-ts_ts(xts_train_windspeed)
ts_plot(ts_train_windspeed)

We must deal with anomalies first.

xts_train_windspeed <- tsclean(xts_train_windspeed)
ts_plot(xts_train_windspeed)

In what follows, interactive plot of both time series are illustrated:

fig <- plot_ly(df_train, type = 'scatter', mode = 'lines')%>%
  add_trace(x = ~date, y = ~meantemp, name = 'MeanTemp')%>%
  add_trace(x = ~date, y = ~wind_speed, name = 'WindSpeed')%>%
  layout(title = 'custom tick labels',legend=list(title=list(text='variable')),
         xaxis = list(dtick = "M1", tickformat= "%b\n%Y"), width = 2000)
## Warning: Specifying width/height in layout() is now deprecated.
## Please specify in ggplotly() or plot_ly()
options(warn = -1)
fig <- fig %>%
  layout(
         xaxis = list(zerolinecolor = '#ffff',
                      zerolinewidth = 2,
                      gridcolor = 'ffff',  tickangle = 0),
         yaxis = list(zerolinecolor = '#ffff',
                      zerolinewidth = 2,
                      gridcolor = 'ffff'),
         plot_bgcolor='#e5ecf6')


fig

We aggregate the windspeed time series by weekly

# Weekly mean temperature
xts_week_train_windspeed <- apply.weekly(xts_train_windspeed,sum)
ts_week_train_windspeed <- ts_ts(xts_week_train_windspeed)
VAR_data <- ts.union(ts_train_meantemp, ts_train_windspeed)
colnames(VAR_data) <- cbind("meantemp","wind_speed")
#VAR_data <- window(ts.union(GDPGrowth, TSpread), start = c(1980, 3), end = c(2012, 4))
v1 <- cbind(xts_week_train_meantemp, xts_week_train_windspeed)
colnames(v1) <- cbind("meantemp","wind_speed")
#lagselect <- VARselect(v1, type = "both")
#lagselect$selection
lagselect <- VARselect(VAR_data, type = "both")
lagselect$selection
## AIC(n)  HQ(n)  SC(n) FPE(n) 
##      8      6      4      8

Let us plot static plots for them individually as well:

ts_plot(ts_week_train_windspeed)

ts_plot(xts_train_windspeed)

Now that we have merged the column meantemp with wind_speed, we use VAR models:

v1 <- na.remove(v1)
tail(v1)
##        meantemp wind_speed
## [203,] 153.7336   37.39762
## [204,] 159.8950   67.64741
## [205,] 143.0019   33.87750
## [206,] 128.2276   21.53095
## [207,] 125.0980   41.68784
## [208,] 119.8610   67.45303
VAR_est <- VAR(y = VAR_data, season=4, type="both")
VAR_est
## 
## VAR Estimation Results:
## ======================= 
## 
## Estimated coefficients for equation meantemp: 
## ============================================= 
## Call:
## meantemp = meantemp.l1 + wind_speed.l1 + const + trend + sd1 + sd2 + sd3 
## 
##   meantemp.l1 wind_speed.l1         const         trend           sd1 
##  9.770688e-01 -1.831148e-02  7.308115e-01 -2.433203e-05  9.295644e-02 
##           sd2           sd3 
##  4.342123e-02  1.138176e-01 
## 
## 
## Estimated coefficients for equation wind_speed: 
## =============================================== 
## Call:
## wind_speed = meantemp.l1 + wind_speed.l1 + const + trend + sd1 + sd2 + sd3 
## 
##   meantemp.l1 wind_speed.l1         const         trend           sd1 
##  0.1238160590  0.3760998074  1.4403595300 -0.0004801852  0.3097544851 
##           sd2           sd3 
##  0.0327325939  0.5358723379
summary(VAR_est)
## 
## VAR Estimation Results:
## ========================= 
## Endogenous variables: meantemp, wind_speed 
## Deterministic variables: both 
## Sample size: 1461 
## Log Likelihood: -6904.721 
## Roots of the characteristic polynomial:
## 0.9733 0.3799
## Call:
## VAR(y = VAR_data, type = "both", season = 4L)
## 
## 
## Estimation results for equation meantemp: 
## ========================================= 
## meantemp = meantemp.l1 + wind_speed.l1 + const + trend + sd1 + sd2 + sd3 
## 
##                 Estimate Std. Error t value Pr(>|t|)    
## meantemp.l1    9.771e-01  6.268e-03 155.893  < 2e-16 ***
## wind_speed.l1 -1.831e-02  1.001e-02  -1.830   0.0675 .  
## const          7.308e-01  1.679e-01   4.352 1.44e-05 ***
## trend         -2.433e-05  1.039e-04  -0.234   0.8148    
## sd1            9.296e-02  1.226e-01   0.758   0.4485    
## sd2            4.342e-02  1.225e-01   0.354   0.7230    
## sd3            1.138e-01  1.226e-01   0.928   0.3534    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## 
## Residual standard error: 1.656 on 1454 degrees of freedom
## Multiple R-Squared: 0.9492,  Adjusted R-squared: 0.949 
## F-statistic:  4532 on 6 and 1454 DF,  p-value: < 2.2e-16 
## 
## 
## Estimation results for equation wind_speed: 
## =========================================== 
## wind_speed = meantemp.l1 + wind_speed.l1 + const + trend + sd1 + sd2 + sd3 
## 
##                 Estimate Std. Error t value Pr(>|t|)    
## meantemp.l1    0.1238161  0.0151937   8.149 7.82e-16 ***
## wind_speed.l1  0.3760998  0.0242597  15.503  < 2e-16 ***
## const          1.4403595  0.4070498   3.539 0.000415 ***
## trend         -0.0004802  0.0002518  -1.907 0.056692 .  
## sd1            0.3097545  0.2972154   1.042 0.297497    
## sd2            0.0327326  0.2969311   0.110 0.912237    
## sd3            0.5358723  0.2972506   1.803 0.071632 .  
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## 
## Residual standard error: 4.013 on 1454 degrees of freedom
## Multiple R-Squared: 0.2284,  Adjusted R-squared: 0.2253 
## F-statistic: 71.75 on 6 and 1454 DF,  p-value: < 2.2e-16 
## 
## 
## 
## Covariance matrix of residuals:
##            meantemp wind_speed
## meantemp     2.7409     0.2722
## wind_speed   0.2722    16.1075
## 
## Correlation matrix of residuals:
##            meantemp wind_speed
## meantemp    1.00000    0.04097
## wind_speed  0.04097    1.00000
summary(VAR_est$varresult)
##            Length Class Mode
## meantemp   12     lm    list
## wind_speed 12     lm    list
summary(VAR_est$varresult$meantemp)$adj.r.squared
## [1] 0.9490318
summary(VAR_est$varresult$wind_speed)$adj.r.squared
## [1] 0.2252582
forecasts <- predict(VAR_est, h=114)
plot(forecasts)

#VAR_EQ1 <- dynlm(ts_train_meantemp ~ #L(ts_train_meantemp, 1:2) + L(ts_train_windspeed, 1:2), #
#                 start = c(2013-01-01), end = c(2012, #4))

#VAR_EQ2 <- dynlm(ts_train_windspeed ~ #L(ts_train_meantemp, 1:2) + L(ts_train_windspeed, 1:2),
#                 start = #decimal_date(ymd("2013-01-01")), end = start = #decimal_date(ymd("2017-01-01")))
Granger_meantemp <- causality(VAR_est, cause = "meantemp")
Granger_meantemp
## $Granger
## 
##  Granger causality H0: meantemp do not Granger-cause wind_speed
## 
## data:  VAR object VAR_est
## F-Test = 66.409, df1 = 1, df2 = 2908, p-value = 5.551e-16
## 
## 
## $Instant
## 
##  H0: No instantaneous causality between: meantemp and wind_speed
## 
## data:  VAR object VAR_est
## Chi-squared = 2.448, df = 1, p-value = 0.1177
Granger_windspeed <- causality(VAR_est, cause = "wind_speed")
Granger_windspeed
## $Granger
## 
##  Granger causality H0: wind_speed do not Granger-cause meantemp
## 
## data:  VAR object VAR_est
## F-Test = 3.3482, df1 = 1, df2 = 2908, p-value = 0.06738
## 
## 
## $Instant
## 
##  H0: No instantaneous causality between: wind_speed and meantemp
## 
## data:  VAR object VAR_est
## Chi-squared = 2.448, df = 1, p-value = 0.1177
FEVD1 <- fevd(VAR_est, n.ahead = 50)
FEVD1
## $meantemp
##        meantemp  wind_speed
##  [1,] 1.0000000 0.000000000
##  [2,] 0.9989928 0.001007226
##  [3,] 0.9980521 0.001947932
##  [4,] 0.9973726 0.002627385
##  [5,] 0.9968980 0.003101993
##  [6,] 0.9965606 0.003439371
##  [7,] 0.9963133 0.003686674
##  [8,] 0.9961262 0.003873790
##  [9,] 0.9959805 0.004019484
## [10,] 0.9958643 0.004135748
## [11,] 0.9957695 0.004230468
## [12,] 0.9956910 0.004308988
## [13,] 0.9956250 0.004375034
## [14,] 0.9955687 0.004431279
## [15,] 0.9955203 0.004479687
## [16,] 0.9954783 0.004521731
## [17,] 0.9954415 0.004558537
## [18,] 0.9954090 0.004590982
## [19,] 0.9953802 0.004619757
## [20,] 0.9953546 0.004645417
## [21,] 0.9953316 0.004668409
## [22,] 0.9953109 0.004689100
## [23,] 0.9952922 0.004707793
## [24,] 0.9952753 0.004724739
## [25,] 0.9952598 0.004740152
## [26,] 0.9952458 0.004754211
## [27,] 0.9952329 0.004767068
## [28,] 0.9952211 0.004778854
## [29,] 0.9952103 0.004789684
## [30,] 0.9952003 0.004799654
## [31,] 0.9951911 0.004808850
## [32,] 0.9951827 0.004817347
## [33,] 0.9951748 0.004825211
## [34,] 0.9951675 0.004832499
## [35,] 0.9951607 0.004839263
## [36,] 0.9951545 0.004845549
## [37,] 0.9951486 0.004851397
## [38,] 0.9951432 0.004856843
## [39,] 0.9951381 0.004861921
## [40,] 0.9951333 0.004866660
## [41,] 0.9951289 0.004871087
## [42,] 0.9951248 0.004875224
## [43,] 0.9951209 0.004879096
## [44,] 0.9951173 0.004882720
## [45,] 0.9951139 0.004886116
## [46,] 0.9951107 0.004889299
## [47,] 0.9951077 0.004892285
## [48,] 0.9951049 0.004895088
## [49,] 0.9951023 0.004897720
## [50,] 0.9950998 0.004900192
## 
## $wind_speed
##          meantemp wind_speed
##  [1,] 0.001678349  0.9983217
##  [2,] 0.005323158  0.9946768
##  [3,] 0.009991521  0.9900085
##  [4,] 0.014905792  0.9850942
##  [5,] 0.019713371  0.9802866
##  [6,] 0.024294436  0.9757056
##  [7,] 0.028619395  0.9713806
##  [8,] 0.032689816  0.9673102
##  [9,] 0.036517286  0.9634827
## [10,] 0.040116077  0.9598839
## [11,] 0.043500641  0.9564994
## [12,] 0.046684789  0.9533152
## [13,] 0.049681454  0.9503185
## [14,] 0.052502668  0.9474973
## [15,] 0.055159599  0.9448404
## [16,] 0.057662617  0.9423374
## [17,] 0.060021352  0.9399786
## [18,] 0.062244756  0.9377552
## [19,] 0.064341159  0.9356588
## [20,] 0.066318317  0.9336817
## [21,] 0.068183461  0.9318165
## [22,] 0.069943335  0.9300567
## [23,] 0.071604234  0.9283958
## [24,] 0.073172041  0.9268280
## [25,] 0.074652255  0.9253477
## [26,] 0.076050021  0.9239500
## [27,] 0.077370154  0.9226298
## [28,] 0.078617166  0.9213828
## [29,] 0.079795286  0.9202047
## [30,] 0.080908479  0.9190915
## [31,] 0.081960464  0.9180395
## [32,] 0.082954734  0.9170453
## [33,] 0.083894569  0.9161054
## [34,] 0.084783050  0.9152170
## [35,] 0.085623074  0.9143769
## [36,] 0.086417364  0.9135826
## [37,] 0.087168483  0.9128315
## [38,] 0.087878842  0.9121212
## [39,] 0.088550711  0.9114493
## [40,] 0.089186227  0.9108138
## [41,] 0.089787403  0.9102126
## [42,] 0.090356136  0.9096439
## [43,] 0.090894215  0.9091058
## [44,] 0.091403324  0.9085967
## [45,] 0.091885053  0.9081149
## [46,] 0.092340902  0.9076591
## [47,] 0.092772284  0.9072277
## [48,] 0.093180534  0.9068195
## [49,] 0.093566912  0.9064331
## [50,] 0.093932606  0.9060674
plot(FEVD1)

7.3 Neural Networks

set.seed(34)
# nnetar() requires a numeric vector or time series object as
# input ?nnetar() can be seen for more info on the function
# nnetar() by default fits multiple neural net models and
# gives averaged results xreg option allows for only numeric
# vectors in nnetar() function
fit_windspeed = nnetar(xts_train_windspeed)
fit_windspeed
## Series: xts_train_windspeed 
## Model:  NNAR(20,10) 
## Call:   nnetar(y = xts_train_windspeed)
## 
## Average of 20 networks, each of which is
## a 20-10-1 network with 221 weights
## options were - linear output units 
## 
## sigma^2 estimated as 4.732
nnetforecast <- forecast(fit_windspeed, h = 114, PI = T)  #Prediction intervals do not come by default in neural net forecasts, in constrast to ARIMA or exponential smoothing model
autoplot(nnetforecast) + theme(plot.title = element_text(hjust = 0.5))

fit_meantemp = nnetar(xts_train_meantemp)
fit_meantemp
## Series: xts_train_meantemp 
## Model:  NNAR(11,6) 
## Call:   nnetar(y = xts_train_meantemp)
## 
## Average of 20 networks, each of which is
## a 11-6-1 network with 79 weights
## options were - linear output units 
## 
## sigma^2 estimated as 2.118
nnetforecast <- forecast(fit_meantemp, h = 114, PI = T)  #Prediction intervals do not come by default in neural net forecasts, in constrast to ARIMA or exponential smoothing model
autoplot(nnetforecast) + theme(plot.title = element_text(hjust = 0.5))